1. Field of the Invention
This invention relates to fifth wheel hitches and, in particular, to a suspension assembly for a fifth wheel that is used to reduce unwanted pitching motions and oscillations in a towing vehicle.
2. Discussion of Related Art
Fifth wheel hitches are used to connect a towed load, such as a trailer, to a towing vehicle, such as a large truck. When the load is in motion, the load creates certain unwanted motions upon the towing vehicle. These unwanted motions include pitching motions in the fore/aft direction of the towing vehicle. When, for example, the towing vehicle starts or stops, speeds or slows, the towed load exerts forces that xe2x80x9cpushxe2x80x9d or xe2x80x9cpullxe2x80x9d on the towing vehicle. Also, unwanted oscillations exerted on the towed vehicle may be transferred to the towing vehicle. For example, if the wheels of the towed vehicle moved over a bump or hole in the road, the resulting oscillatory motions would be transferred to the towing vehicle. These motions are transferred from the road surface through the trailer suspension into the trailer structure, through the fifth wheel and into the towing vehicle. Just as towed vehicle motion forces can be transferred to the towing vehicle, likewise, motion forces affecting the towing vehicle also may be transmitted to the towed load.
Conventional fifth wheels have several disadvantages in that they do not contain any mechanism for damping the unwanted pitching motions and oscillations transferred between the towing vehicle and the towed load. These unwanted motions result in a more unpleasant and dangerous ride for those in the towing vehicle. These unwanted motions also put the cargo of the towed vehicle at risk, for example, if the cargo is fragile, not well secured, or an animal, such as a horse or other livestock.
In order to overcome the inherent drawbacks in conventional fifth wheel assemblies, various fifth wheel suspensions have been proposed. For example, U.S. Pat. Nos. 2,093,761 and 4,991,864 each illustrate a fifth wheel base mounted on a pair of longitudinal rods and capable of movement along the rods in the longitudinal direction of the vehicle. Springs disposed about the rods dampen movement of the fifth wheel base along the rods. These disclosed suspensions dampen movement between the towing and towed vehicles. The amount of damping provided by the disclosed suspensions, however, is limited.
The inventors herein have recognized that there is a need for a fifth wheel suspension that will minimize or eliminate one or more of the above-mentioned deficiencies.
The present invention provides a suspension assembly for damping movement between a towing vehicle and a towed vehicle.
A suspension assembly in accordance with the present invention includes first and second rods mounted to a frame of the towing vehicle, each of the first and second rods having a longitudinal axis extending in the longitudinal direction of a towing vehicle. A fifth wheel base is coupled to the towed vehicle and mounted on the first and second rods for movement in the longitudinal (fore/aft) direction of the towing vehicle. The fifth wheel base defines first and second fluid chambers that are disposed about the first and second rods. Finally, the assembly includes first and second pistons disposed within the first and second fluid chambers. The suspension assembly may further include springs disposed about the first and second rods on either side of the fifth wheel base.
A suspension assembly in accordance with the present invention represents a significant improvement as compared to conventional suspension assemblies for damping movement between a towing vehicle and a towed vehicle. In particular, the inventive suspension assembly reduces both unwanted pitching motions and oscillations, making the movement of both the towing vehicle and towed vehicle more comfortable and safer for all occupants. The present invention has a multi-faceted approach to dampening unwanted motions, both simultaneously reducing pitching motions in the fore/aft direction by allowing the towed vehicle to move in the fore/aft direction relative to the towing vehicle and dampening oscillations through the use of fluid chambers and pistons.
These and other features and objects of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.